Microstructured carbonatable calcium silicate clinkers and methods thereof

ABSTRACT

The invention provides novel, microstructured clinker and cement materials that are characterized by superior grindability and reactivity. The disclosed clinker and cement materials are based on carbonatable calcium silicate and can be made from widely available, low cost raw materials via a process suitable for large-scale production. The method of the invention is flexible in equipment and processing requirements and is readily adaptable to manufacturing facilities of conventional Portland cement.

PRIORITY CLAIMS AND RELATED PATENT APPLICATIONS

This application claims the benefit of priority from U.S. ProvisionalApplication Ser. Nos. 62/136,201 and 62/136,208, both filed on Mar. 20,2015, the entire content of each of which is incorporated herein byreference in its entirety.

FIELD OF THE INVENTION

The invention generally relates to calcium silicate compositions. Moreparticularly, the invention relates to novel microstructuredcarbonatable calcium silicate compositions (e.g., clinkers, cements),and methods for their manufacture and uses, for example, in a variety ofconcrete components in the infrastructure, construction, pavement andlandscaping industries.

BACKGROUND OF THE INVENTION

Concrete is the most consumed man-made material in the world. A typicalconcrete is made by mixing Portland cement, water and aggregates such assand and crushed stone. Portland cement is a synthetic material made byburning a mixture of ground limestone and clay, or materials of similarcomposition in a rotary kiln at a sintering temperature of 1450° C.Portland cement manufacturing is not only an energy-intensive process,but one which releases considerable quantities of greenhouse gas (CO₂).The cement industry accounts for approximately 5% of globalanthropogenic CO₂ emissions. More than 60% of this CO₂ comes from thechemical decomposition, or calcination of limestone.

There has been growing effort to reduce total CO₂ emissions within thecement industry. According to a proposal by the International EnergyAgency, the cement industry needs to reduce its CO₂ emissions from 2.0Gt in 2007 to 1.55 Gt by 2050. This represents a daunting task because,over this same period, cement production is projected to grow from 2.6Gt to 4.4 Gt.

To meet this formidable challenge, a revolutionary approach to cementproduction was developed that significantly reduces the energyrequirement and CO₂ emissions of a cement plant. The unique cement iscomprised of carbonatable calcium silicate compositions and is made fromwidely available, low cost raw materials and offers the ability topermanently and safely sequester CO₂ while being adaptable and flexiblein equipment and production requirements, allowing manufacturers ofconventional cement to easily convert to the new platform.

“Clinker” refers to lumps or nodules produced by heating in a rotarykiln at high temperature a mixture of raw materials including limestoneand alumino-silicate materials such as clay (˜1,450° C. in Portlandcement). Cement clinker is ground to a fine powder for use in manycement products.

Besides reactivity, clinker grindability is an important measure of theclinker quality. Considerable energy is consumed at a cement plant forclinker grinding. Improved clinker grindability thus increases grindingefficiency and reduces energy consumption. For the carbonatable calciumsilicate-based cement production, clinker grindability is an importantproperty. Unlike in the case of Portland cement, grindability of calciumsilicate-based clinker is not understood nor is grindabilityoptimization achieved.

Thus, it is important to develop suitable clinker productionmethodologies that yield favored clinker microstructures and desiredgrindability profile and reactivity.

SUMMARY OF THE INVENTION

The invention provides a novel, microstructured clinker and cementmaterials that are characterized by superior grindability andreactivity. The disclosed clinker and cement materials are based oncarbonatable calcium silicate and can be made from widely available, lowcost raw materials via a process suitable for large-scale production.The method of the invention is flexible in equipment and processingrequirements and is readily adaptable at manufacturing facilities ofconventional Portland cement.

These disclosed carbonatable calcium silicate clinker and cementcompositions can be used in a variety of concrete applications such asin construction, pavements and landscaping, and infrastructure withreduced equipment need, improved energy consumption, and more desirablecarbon footprint.

The heterogeneous nature of the microstructures of clinker gives rise tounique clinker grinding properties due to the differences in density andhardness of the various phase regions. Lower density layers act as apath of least resistance for fracture during crushing and grindingoperations, resulting in not only reduced energy consumption but alsomore reactive phases being exposed upon grinding. The layeredmicrostructures may also give rise to particle morphologies thatfacilitate carbonation and formation of stronger composite materials.

In one aspect, the invention generally relates to a non-hydraulicclinker material, which includes particles of uncarbonatable silica(SiO₂) dispersed in a matrix comprising at least one carbonatablecalcium silicate phase comprising at least one of wollastonite andpseudowollastonite. As disclosed herein, the clinker material of theinvention is carbonatable to yield a composite material via carbonationwith CO₂.

In another aspect, the invention generally relates to a method formaking a clinker material disclosed herein. The method includes: mixingone or more precursors to obtain a blended precursor composition whereinelemental Ca and elemental Si are present at an atomic ratio from about0.8 to about 1.2 and metal oxides of Al, Fe and Mg are present at about10% or less by mass; and heating the blended precursor composition to atemperature between about 800° C. and about 1400° C. for a sufficienttime to produce the clinker material.

Various raw materials may be used as precursors to produce the clinkermaterial of the invention. For example, suitable raw materials includelimestone, sand, silts, sandstones, silica-rich clays, diatomaceousearths, marl, fly ash, silica fume, etc.

In yet another aspect, the invention relates to a powdery materialproduced by grinding the clinker material of the invention. In certainpreferred embodiments, the powdery material is characterized by a meanparticle size (d50) of about 8 μm to about 25 μm, with 10% of particles(d10) sized below about 0.1 μm to about 3 μm, and 90% of particles (d90)sized between about 30 μm to about 100 μm.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and features of the invention can be better understood withreference to the drawings described below, and the claims. The drawingsare not necessarily to scale, emphasis instead generally being placedupon illustrating the principles of the invention. In the drawings, likenumerals are used to indicate like parts throughout the various views.

FIG. 1. A backscattered electron (BSE) Image of a cement clinker fromExperimental Cement 1. Layers of low brightness unreactive silica bandedby progressively brighter reactive phases are visible.

FIG. 2. A backscattered electron (BSE) Image of a cement clinker fromExperimental Cement 1. Layers of low brightness unreactive silica bandedby progressively brighter reactive phases are visible. Phases wereidentified by EDS to be silica (1), amorphous phase (2). wollastonite orpseudowollastonite (3) and rankinite (4).

FIG. 3. A high magnification image of a calcium-rich region of cementclinker from Experimental Cement 1. This region contained discretebelite (1) and rankinite (2) regions with some intergranular materialwith an amorphous composition.

FIG. 4. A backscattered electron (BSE) Image of unreacted cementparticles. The image displays a large particle composed of highbrightness reactive phases (1). A similarly sized particle shows adistribution of multiple phases with a surface of high brightnessreactive material, a band of medium brightness amorphous phases (2) anda core of low brightness SiO₂ phase (3). Smaller single-phase particlesare also visible.

FIG. 5. BSE Image of unreacted cement particles. A large number ofparticle types are evident. Two phase multi-phase reactive—partiallyreactive and partially reactive—inert particles (1), three phasereactive—partially reactive—inert (2), and reactive—void (3) particlescan be seen.

FIG. 6. False color composite micrograph depicting various particles ofExperimental Cement 1. Single and multi-phase particles of manycompositions are visible.

FIG. 7. False color composite micrograph depicting various particles ofExperimental Cement 1. Single and multi-phase particles of manycompositions are visible.

FIG. 8. False color composite micrograph depicting various particles ofExperimental Cement 1. Single and multi-phase particles of manycompositions are visible.

FIG. 9. A backscattered electron (BSE) Image of a cement clinker fromExperimental Cement 2. Layers of low brightness unreactive silica bandedby progressively brighter reactive phases are visible.

FIG. 10. A backscattered electron (BSE) Image of a cement clinker fromExperimental Cement 2. Layers of low brightness unreactive silica bandedby progressively brighter reactive phases are visible.

FIG. 11. A backscattered electron (BSE) image of a cement clinker fromExperimental Cement 2.

FIG. 12. An X-Ray map of FIG. 11 indicating the location of Si. The mapindicates that the dark regions from FIG. 11 are rich in Si and that Siis less abundant at points distant from these areas.

FIG. 13. An X-Ray map of FIG. 11 indicating the location of Ca. The mapindicates that the abundance of Ca increases in distinct increments fromthe Si rich regions.

FIG. 14. An X-Ray map of potassium indicating that the potassium isconcentrated around the edge of the silica particles.

DETAILED DESCRIPTION OF THE INVENTION

The invention provides a novel carbonatable clinker material based oncalcium silicate and a ground powdery composition produced therefrom,which serves as a revolutionary replacement for conventional cements.These materials can be produced and utilized with significantly reducedenergy requirement and CO₂ emissions. The disclosed carbonatable calciumsilicate-based clinker materials are made from widely available, lowcost raw materials by a process suitable for large-scale production withflexible equipment and production requirements.

A wide variety of applications can benefit from the invention, fromconstruction, pavements and landscaping, to infrastructure andtransportation through improved energy consumption and more desirablecarbon footprint.

In one aspect, the invention generally relates to a non-hydraulicclinker material, that includes particles of uncarbonatable silica(SiO₂) dispersed in a matrix comprising at least one carbonatablecalcium silicate phase comprising at least one of wollastonite andpseudowollastonite, i.e., one or more of CS (wollastonite orpseudowollastonite).

In certain embodiments of the clinker material, the matrix comprisesrankinite (C3S2, Ca₃Si₂O₇) and/or belite (C2S, Ca₂SiO₄). The C2S phasepresent within the calcium silicate composition may exist in anyα-Ca₂SiO₄, β-Ca₂SiO₄ or γ-Ca₂SiO₄ polymorph or combination thereof.

In certain embodiments, the clinker material further includes anintermediate layer, comprising melilite((Ca,Na,K)₂(Al,Mg,Fe)[(Al,Si)SiO₇]) and/or an amorphous phase andsurrounding the particles of uncarbonatable silica. The clinker may alsoinclude quantities of phases without the ability to significantlycarbonate, such as ferrite type minerals (ferrite or brownmillerite orC4AF) with the general formula Ca₂(Al,Fe³⁺)₂O₅.

The clinker may also include small or trace (<10% by mass of each phase)quantities of residual CaO (lime) and SiO₂ (silica).

The clinker may also include small or trace (<10% by mass) quantities ofC3S (alite, Ca₃SiO₅).

The metal oxides of Al, Fe and Mg contained within the clinker aregenerally controlled to be less than about 10% (by total oxide mass) ofthe total clinker mass. In certain embodiments, the clinker has about 8%or less of metal oxides of Al, Fe and Mg (by total oxide mass) of thetotal clinker mass. In certain embodiments, the clinker has about 5% orless of metal oxides of Al, Fe and Mg (by total oxide mass) of the totalclinker mass. In certain embodiments depending on the application, theclinker may have more than 10% (e.g., about 10% to about 30%) of metaloxides of Al, Fe and Mg (by total oxide mass) of the total clinker mass.In certain embodiments, the clinker has about 30% or less of metaloxides of Al, Fe and Mg (by total oxide mass) of the total clinker mass.

The clinker material may be comprised of one or more of amorphous phasesand crystalline phases, which may exist in discrete or joint regions orlayers.

The amorphous phase may incorporate Al, Fe and Mg ions and otherimpurity ions present in the raw materials. In certain embodiments, theclinker's microstructural matrix includes one or more componentsselected from Al₂O₃, Fe₂O₃, MgO, K₂O and Na₂O. For example, theintermediate layer may include an amorphous phase comprising one or morecomponents selected from Al₂O₃, Fe₂O₃, MgO, K₂O and Na₂O.

The uncarbonatable silica particles may have any suitable morphology andsizes. For example, the uncarbonatable silica particles may havediameters from about 0.1 μm to about 1,000 μm (e.g., about 0.5 μm toabout 1,000 μm, about 1.0 μm to about 1,000 μm, about 10 μm to about1,000 μm, about 25 μm to about 1,000 μm, about 50 μm to about 1,000 μm,about 100 μm to about 1,000 μm, about 0.1 μm to about 500 μm, about 0.1μm to about 100 μm, about 0.1 μm to about 50 μm, about 1.0 μm to about500 μm, about 10 μm to about 500 μm, about 25 μm to about 500 μm, about25 μm to about 200 μm).

The intermediate layer may have any suitable morphology and sizes. Forexample, the intermediate layer may have a thickness from about 0.1 μmto about 250 μm (e.g., from about 0.5 μm to about 250 μm, from about 1.0μm to about 250 μm, from about 5.0 μm to about 250 μm, from about 10 μmto about 250 μm, from about 25 μm to about 250 μm, from about 0.1 μm toabout 100 μm, from about 0.1 μm to about 50 μm, from about 1.0 μm toabout 100 μm, from about 1.0 μm to about 50 μm, from about 1.0 μm toabout 25 μm).

In the clinker material, the amorphous phase may account for anysuitable percentage, for example, at about 10% or more by volume of thetotal solid phases (e.g., at about 15% or more, at about 20% or more, atabout 25% or more, at about 30% or more, at about 40% or more, at about45% or more, at about 50% or more, at about 55% or more, at about 60% ormore, at about 65% or more, at about 70% or more, at about 75% or more,at about 80% or more by volume of the total solid phases).

In the clinker material, the crystalline phase may account for anysuitable percentage, for example, at about 30% or more by volume of thetotal solid phases (e.g., at about 30% or more, at about 35% or more, atabout 40% or more, at about 45% or more, at about 50% or more, at about55% or more, at about 60% or more, at about 65% or more, at about 70% ormore, at about 75% or more, at about 80% or more, at about 85% or more,at about 90% or more, at about 95% or more, by volume of the total solidphases).

In certain preferred embodiments of the clinker material, the atomicratio of elemental Ca to elemental Si of the calcium silicatecomposition is from about 0.80 to about 1.20. In certain preferredembodiments, the atomic ratio of Ca to Si of the composition is fromabout 0.85 to about 1.15. In certain preferred embodiments, the atomicratio of Ca to Si of the composition is from about 0.90 to about 1.10.In certain preferred embodiments, the atomic ratio of Ca to Si of thecomposition is from about 0.95 to about 1.05. In certain preferredembodiments, the atomic ratio of Ca to Si of the composition is fromabout 0.98 to about 1.02. In certain preferred embodiments, the atomicratio of Ca to Si of the composition is from about 0.99 to about 1.01.

In certain preferred embodiments, the clinker is suitable forcarbonation with CO₂ at a temperature of about 30° C. to about 90° C. toform CaCO₃, under an atmosphere of water and CO₂ having a pressure inthe range from ambient atmospheric pressure to about 150 psi aboveambient and having a CO₂ concentration ranging from about 10% to about99% for about 1 hour to about 150 hours, with a mass gain of about 10%or more. In certain preferred embodiments, the clinker is suitable forcarbonation with CO₂ at a temperature of about 40° C. to about 80° C. toform CaCO₃, under an atmosphere of water and CO₂ having a pressure inthe range from ambient atmospheric pressure to about 40 psi aboveambient and having a CO₂ concentration ranging from about 50% to about95% for about 10 hour to about 50 hours, with a mass gain of about 10%or more, preferably 20% or more. The mass gain reflects the netsequestration of CO₂ in the carbonated products. Thus, carbonatation isadvantageously performed under an atmosphere of water and CO₂.Carbonatation is advantageously performed at a temperature of about 30°C. to about 90° C. to form CaCO₃. The pressure may range from ambientatmospheric pressure to about 150 psi above ambient. The CO₂concentration may range from about 10% to about 99%. The carbonatationmay last for about 1 hour to about 150 hours. The mass gain is of about10% or more, preferably 20% or more, or more preferably 30% or more.

In certain preferred embodiments, the composition is suitable forcarbonation with CO₂ at a temperature of about 30° C. to about 90° C.(e.g., about 40° C. to about 90° C., about 50° C. to about 90° C., about60° C. to about 90° C., about 30° C. to about 80° C., about 30° C. toabout 70° C., about 30° C. to about 60° C., about 40° C. to about 80°C., about 40° C. to about 70° C., about 40° C. to about 60° C.) to formCaCO₃ with mass gain of 10% or more (e.g., 15% or more, 20% or more, 25%or more, 30% or more).

It is noted that preferably the carbonatable calcium silicate-basedclinker compositions of the invention do not hydrate. However, minoramounts of hydratable calcium silicate phases (e.g., C2S, C3S and CaO)may be present. C2S exhibits slow kinetics of hydration when exposed towater and is quickly converted to CaCO₃ during CO₂ curing processes. C3Sand CaO hydrate quickly upon exposure to water and thus should each belimited to less than about 10% by mass.

As disclosed herein, the clinker material of the invention iscarbonatable to yield a composite material via carbonation with CO₂. Thegeneration of binding strength is the result of and is controlled bycarbonation of various reactive phases in the clinker material whenexposed to CO₂ under specific curing regimes.

The CaCO₃ produced from the CO₂ carbonation reactions disclosed hereinmay exist as one or more of several CaCO₃ polymorphs (e.g., calcite,aragonite, and vaterite). The CaCO₃ are preferably in the form ofcalcite but may also be present as aragonite or vaterite or as acombination of two or three of the polymorphs (e.g., calcite/aragonite,calcite/vaterite, aragonite/vaterite or calcite/aragonite/vaterite).

In another aspect, the invention generally relates to a method formaking a clinker material disclosed herein. The method includes: mixingone or more precursors to obtain a blended precursor composition whereinelemental Ca and elemental Si are present at an atomic ratio from about0.8 to about 1.2 and metal oxides of Al, Fe and Mg are present at about30% or less by mass; and heating the blended precursor composition to atemperature between about 800° C. and about 1400° C. for a sufficienttime to produce the clinker material.

Various raw materials may be used as precursors to produce the clinkermaterial of the invention. For example, suitable raw materials includelimestone, sand, silts, sandstones, silica-rich clays, diatomaceousearths, marl, fly ash, silica fume, etc.

As disclosed herein, to make the clinker material of the invention, theprecursors atomic ratio of elemental Ca to elemental Si of the calciumsilicate composition is to be kept at a select range, preferably fromabout 0.80 to about 1.20 (e.g., from about 0.85 to about 1.15, fromabout 0.90 to about 1.10, from about 0.95 to about 1.05, from about 0.98to about 1.02, from about 0.99 to about 1.01).

The blended precursor composition is heated to a temperature and for asufficient time to produce the clinker material having themicrostructure disclosed here. For example, the blended precursorcomposition is heated to a temperature between about 800° C. and about1,400° C. (e.g., between about 800° C. and about 1,300° C., betweenabout 800° C. and about 1,200° C., between about 800° C. and about1,100° C., between about 800° C. and about 1,000° C., between about 900°C. and about 1,400° C., between about 1,000° C. and about 1,400° C.,between about 1,100° C. and about 1,400° C., between about 1,200° C. andabout 1,400° C., between about 900° C. and about 1,300° C., betweenabout 900° C. and about 1,300° C., between about 1,100° C. and about1,200° C., between about 1,200° C. and about 1,300° C.).

To produce the clinker material, the blended precursor composition isheated for a period sufficient to achieve the desired microstructure,for example, for a period from about 10 minutes to about 80 hours (e.g.,from about 1 hour to about 80 hours, from about 5 hours to about 80hours, from about 10 hours to about 80 hours, from about 15 hours toabout 80 hours, from about 20 hours to about 80 hours, from about 1 hourto about 60 hours, from about 1 hour to about 40 hours, from about 1hour to about 30 hours, from about 1 hour to about 20 hours, from about1 hour to about 10 hours, from about 1 hour to about 5 hours, from about5 hours to about 60 hours, from about 5 hours to about 20 hours, fromabout 5 hours to about 10 hours, from about 10 minutes to about 5 hours,from about 15 minutes to about 3 hours, from about 20 minutes to about 2hours).

In preferred embodiments, heating the blended precursor composition isconducted under atmospheric pressure.

In yet another aspect, the invention relates to a powdery materialproduced by grinding the clinker material of the invention.

In certain preferred embodiments, the powdery material (also referred toas “cement”) is comprised of cement particles, which are characterizedby a mean particle size (d50) of about 8 μm to about 25 μm, with 10% ofparticles (d10) sized below about 0.1 μm to about 3 μm, and 90% ofparticles (d90) sized between about 30 μm to about 100 μm.

In certain embodiments, the ratio of d90:d10 (e.g., a d90:d10 ratio of30 or higher) is selected to allow improved powder flow or decreasedwater demand for casting. In certain embodiments, the ratio of d50:d10(e.g., a d50:d10 ratio of 12 or lower) is selected to allow improvedreactivity, improved packing, or decreased water demand for casting. Incertain embodiments, the ratio of d90:d50 (e.g., a d50:d10 ratio of 3 orhigher) is selected to allow improved the reactivity, improved packing,or decreased water demand for casting.

Cement particles exhibit various microstructures, which may becategorized into two groups: single phase particles and multi-phaseparticles. Single phase particles may exist in various forms including:(i) reactive (carbonatable) wollastonite (CaSiO₃), rankinite (Ca₃Si₂O₇)and C2S (Ca₂SiO₄); (ii) partially reactive amorphous phases of variablecompositions; and (iii) inert (uncarbonatable or insignificantcarbonation) phases such as melilite ((Ca,Na,K)₂[(Mg,Fe²⁺,Fe³⁺,Al,Si)₃O₇]), ferrite (Ca₂(Al,Fe³⁻)₂O₇) and crystalline silica(SiO₂).

TABLE 1 Reaction Behavior of Various Phases Category Constituent phasesReaction behavior Reactive CaSiO₃ Reacts extensively Ca₃Si₂O₇ with CO₂.Ca₂SiO₄ CaO Partially Amorphous Reacts with CO₂ to Reactive a degreedictated by its composition. Inert SiO₂ Does not react withCa₂(Al,Fe³⁺)O₅ CO₂ or reacts to an (Ca,Na,K)₂ (Al,Mg,Fe)[(Al,Si)SiO₇]insignificant degree.

Multi-phase particles may exist in various forms including: (i)“reactive-reactive”, i.e., a combination of two or more reactive phases(e.g., CaSiO₃, Ca₃Si₂O₇, Ca₂SiO₃); (ii) “reactive-inert”, i.e., acombination of at least one reactive phase (e.g., CaSiO₃, Ca₃Si₂O₇,Ca₂SiO₃) with at least one inert phase (e.g., (Ca,Na,K)₂[(Mg,Fe²⁺,Fe³⁺,Al,Si)₃O₇], SiO₂); (iii) “inert-inert”, i.e., a combination oftwo or more inert phases (e.g., (Ca,Na,K)₂[(Mg, Fe²⁺,Fe³⁺,Al,Si)₃O₇],SiO₂); (iv) “reactive-partially reactive”, i.e., a combination of atleast one reactive phase (e.g., CaSiO₃, Ca₃Si₂O₇, Ca₂SiO₃) with apartially reactive amorphous phase; (v) “inert-partially reactive”,i.e., a combination of at least one inert phase (e.g., (Ca,Na,K)₂[(Mg,Fe²⁻,Fe³⁺,Al,Si)₃O₇], SiO₂) with a partially reactive amorphous phase;(vi) “reactive-slightly reactive-inert”, i.e., a combination of at leastone reactive phase (e.g., CaSiO₃, Ca₃Si₂O₇, Ca₂SiO₃) with at least oneinert phase (e.g., (Ca,Na,K)₂[(Mg, Fe²⁻,Fe³⁺,Al,Si)₃O₇], SiO₂) and apartially reactive amorphous phase; and (vii) void-containing particles,wherein a particle from one of the categories above that is not fullydense and has internal or surface connected voids.

“Reactive” and “carbonatable” are used interchangeably herein to referto a material that is reactive with CO₂ via a carbonation reaction undera condition disclosed herein. A material is “inert” or “uncarbonatable”if it is unreactive with CO₂ via a carbonation reaction under acondition disclosed herein. “Partially reactive” refers to a phase aportion of which is reactive. “Slightly reactive” refers to a phase thatis not completely inert but has an insignificant or negligiblereactivity. The terms “reactive phase” and “carbonatable phase” are usedinterchangeably to refer to a material phase that is carbonatable asdefined herein. The terms “inert phase” and “uncarbonatable phase” areused interchangeably to refer to a material phase that is uncarbonatableas defined herein. Exemplary carbonatable or reactive phases include CS(wollastonite or pseudowollastonite, and sometimes formulated CaSiO₃ orCaO.SiO₂), C3S2 (rankinite, and sometimes formulated as Ca₃Si₂O₇ or3CaO.2SiO₂), C2S (belite, β-Ca₂SiO₄ or larnite, Ca₇Mg(SiO₄)₄ orbredigite, α-Ca₂SiO₄ or γ-Ca₂SiO₄, and sometimes formulated as Ca₂SiO₄or 2CaO.SiO₂). Amorphous phases can also be carbonatable depending ontheir compositions. Exemplary uncarbonatable or inert phases includemelilite ((Ca,Na,K)₂[(Mg, Fe²⁺,Fe³⁺,Al,Si)₃O₇]) and crystalline silica(SiO₂).

The powdery material may have any suitable bulk density, for example, abulk density from about 0.5 g/mL to about 3.5 g/mL (loose, e.g., 0.5g/mL, 1.0 g/mL, 1.5 g/mL, 2.0 g/mL, 2.5 g/mL, 2.8 g/mL, 3.0 g/mL, 3.5g/mL) and about 1.0 g/mL to about 1.2 g/mL (tapped), a Blaine surfacearea from about 150 m²/kg to about 700 m²/kg (e.g., 150 m²/kg, 200m²/kg, 250 m²/kg, 300 m²/kg, 350 m²/kg, 400 m²/kg, 450 m²/kg, 500 m²/kg,550 m2/kg, 600 m2/kg, 650 m2/kg, 700 m2/kg).

The powdery material may be produced with a preferred reactivityprofile. In certain embodiments, for example, the powdery material ischaracterized by a surface at least 10% covered with a carbonatablephase. In certain embodiments, the powdery material is characterized bya surface at least 20% covered with a carbonatable phase. In certainembodiments, the powdery material is characterized by a surface at least30% covered with a carbonatable phase. In certain embodiments, thepowdery material is characterized by a surface at least 40% covered witha carbonatable phase. In certain embodiments, the powdery material ischaracterized by a surface at least 50% covered with a carbonatablephase. In certain embodiments, the powdery material is characterized bya surface at least 60% covered with a carbonatable phase. In certainembodiments, the powdery material is characterized by a surface at least70% covered with a carbonatable phase. In certain embodiments, forexample, the powdery material is characterized by a surface at least 80%covered with a carbonatable phase. In certain embodiments, the powderymaterial is characterized by a surface at least 90% covered with acarbonatable phase. In certain embodiments, the powdery material ischaracterized by a surface at least 95% covered with a carbonatablephase. In certain embodiments, the powdery material is characterized bya surface substantially fully covered with a carbonatable phase.

The various reactive (carbonatable) phases may account for any suitableportions of the overall reactive phases. In certain preferredembodiments, the reactive phases of CS are present at about 5 wt % toabout 60 wt % (e.g., about 10 wt % to about 60 wt %, about 20 wt % toabout 60 wt %, about 25 wt % to about 60 wt %, about 30 wt % to about 60wt %, about 35 wt % to about 60 wt %, about 40 wt % to about 60 wt %,about 5 wt % to about 50 wt %, about 5 wt % to about 40 wt %, about 5 wt% to about 30 wt %, about 5 wt % to about 25 wt %, about 5 wt % to about20 wt %); C3S2 in about 5 wt % to 50 wt % (e.g., about 10 wt % to 50 wt%, about 15 wt % to 50 wt %, about 20 wt % to 50 wt %, about 30 wt % to50 wt %, about 40 wt % to 50 wt %, about 5 wt % to 40 wt %, about 5 wt %to 30 wt %, about 5 wt % to 25 wt %, about 5 wt % to 20 wt %, about 5 wt% to 15 wt %); and C2S in about 5 wt % to 60 wt % (e.g., about 10 wt %to about 60 wt %, about 20 wt % to about 60 wt %, about 25 wt % to about60 wt %, about 30 wt % to about 60 wt %, about 35 wt % to about 60 wt %,about 40 wt % to about 60 wt %, about 5 wt % to about 50 wt %, about 5wt % to about 40 wt %, about 5 wt % to about 30 wt %, about 5 wt % toabout 25 wt %, about 5 wt % to about 20 wt %, about 5 wt % to about 20wt %), and C in about 0 wt % to 3 wt % (e.g., 0 wt %, 1 wt % or less, 2wt % or less, 3 wt % or less, about 1 wt % to 2 wt %, about 1 wt % to 3wt %, about 2 wt % to 3 wt %).

As used herein, the term “calcium silicate composition” generally refersto naturally-occurring minerals or synthetic materials that arecomprised of one or more of a group of calcium silicate phases includingCS (wollastonite or pseudowollastonite, and sometimes formulated CaSiO₃or CaO.SiO₂), C3S2 (rankinite, and sometimes formulated as Ca₃Si₂O₇ or3CaO.2SiO₂), C2S (belite, β-Ca₂SiO₄ or larnite, Ca₇Mg(SiO₄)₄ orbredigite, α-Ca₂SiO₄ or γ-Ca₂SiO₄, and sometimes formulated as Ca₂SiO₄or 2CaO.SiO₂), a calcium-silicate based amorphous phase, each of whichmaterial may include one or more other metal ions and oxides (e.g.,aluminum, magnesium, iron or manganese oxides), or blends thereof, ormay include an amount of magnesium silicate in naturally-occurring orsynthetic form(s) ranging from trace amount (1% or less) to about 50% ormore by weight.

It should be understood that, calcium silicate compositions, phases andmethods disclosed herein can be adopted to use suitable magnesiumsilicate phases in place of or in addition to calcium silicate phases.As used herein, the term “magnesium silicate” refers tonaturally-occurring minerals or synthetic materials that are comprisedof one or more of a groups of magnesium-silicon-containing compoundsincluding, for example, Mg₂SiO₄ (also known as “forsterite”) andMg₃Si₄O₁₀(OH)₂ (also known as “talc”), which material may include one ormore other metal ions and oxides (e.g., calcium, aluminum, iron ormanganese oxides), or blends thereof, or may include an amount ofcalcium silicate in naturally-occurring or synthetic form(s) rangingfrom trace amount (1% or less) to about 50% or more by weight.

A major utility of the clinker material of the invention is that theclinker, usually after being ground into powdery cement, can becarbonated to form composite materials that are useful in a variety ofapplications. A variety of composite products can be produced by aprocess that does not require autoclave(s) and is suitable forcontinuous, large-scale production. The production methods are muchimproved over conventional concretes in terms of both economics andenvironmental impact.

The carbonation, for example, may be carried out by reacting the cementof the invention with CO₂ via a controlled Hydrothermal Liquid PhaseSintering (HLPS) process to create bonding strength that hold togetherthe various components of the composite material. Discussions of variousfeatures of HLPS can be found in U.S. Pat. No. 8,114,367, U.S. Pub. No.US 2009/0143211 (application Ser. No. 12/271,566), U.S. Pub. No. US2011/0104469 (application Ser. No. 12/984,299), U.S. Pub. No.2009/0142578 (application Ser. No. 12/271,513), U.S. Pub. No.2013/0122267 (application Ser. No. 13/411,218), U.S. Pub. No.2012/0312194 (application Ser. No. 13/491,098), WO 2009/102360(PCT/US2008/083606), WO 2011/053598 (PCT/US2010/054146), WO 2011/090967(PCT/US2011/021623), U.S. Provisional Patent Application No. 61/708,423filed Oct. 1, 2012, and U.S. patent application Ser. Nos. 14/045,758,14/045,519, 14/045,766, 14/045,540, all filed Oct. 3, 2013, U.S. patentapplication Ser. Nos. 14/207,413, 14/207,421, filed Mar. 12, 2014, U.S.patent applicaton Ser. Nos. 14/207,920, 14/209,238, filed Mar. 13, 2014,U.S. patent applicaton Ser. Nos. 14/295,601, 14/295,402, filed Jun. 4,2014, each of which is expressly incorporated herein by reference in itsentirety for all purposes.

Any suitable aggregates may be used to form composite materials from thecarbonatable composition of the invention, for example, calciumoxide-containing or silica-containing materials. Exemplary aggregatesinclude inert materials such as trap rock, construction sand,pea-gravel. In certain preferred embodiments, lightweight aggregatessuch as perlite or vermiculite may also be used as aggregates. Materialssuch as industrial waste materials (e.g., fly ash, slag, silica fume)may also be used as fine fillers.

The plurality of aggregates may have any suitable mean particle size andsize distribution. In certain embodiments, the plurality of aggregateshas a mean particle size in the range from about 0.25 mm to about 25 mm(e.g., about 5 mm to about 20 mm, about 5 mm to about 18 mm, about 5 mmto about 15 mm, about 5 mm to about 12 mm, about 7 mm to about 20 mm,about 10 mm to about 20 mm, about ⅛″, about ¼″, about ⅜″, about ½″,about ¾″).

Chemical admixtures may also be included in the composite material, forexample, plasticizers, superplasticizers, retarders, accelerators,dispersants and other rheology-modifying agents. Certain commerciallyavailable chemical admixtures such as Glenium™ 7500 by BASF® Chemicalsand Acumer™ by Dow Chemical Company may also be included. In certainembodiments, one or more pigments may be evenly dispersed orsubstantially unevenly dispersed in the bonding matrices, depending onthe desired composite material. The pigment may be any suitable pigmentincluding, for example, oxides of various metals (e.g., black ironoxide, cobalt oxide and chromium oxide). The pigment may be of any coloror colors, for example, selected from black, white, blue, gray, pink,green, red, yellow and brown. The pigment may be present in any suitableamount depending on the desired composite material, for example in anamount ranging from about 0.0% to about 10% by weight of cement.

EXAMPLES

Samples of carbonatable calcium silicate clinkers and cements wereembedded in epoxy, polished and coated with carbon to obtain informationon the distribution of phases within the clinker or within individualparticles. The samples were analyzed by a scanning electron microscope(SEM) in backscattered electron (BSE) imaging mode. The contrast of eachphase is related to that phase's stoichiometry, where more dense phasescontaining high mean atomic number elements will appear more brightlythan a less dense phase with a lower mean atomic number. The contrast ofthe various phases can be related by comparison of the BSE contrastfactor η calculated using the mean atomic number Z of each phase.

$\begin{matrix}{\eta = {\frac{\ln \; \overset{\_}{Z}}{6} - {\frac{1}{4}\left( {\overset{\_}{Z} \geq 10} \right)}}} & \left( {{Equation}\mspace{14mu} 1} \right)\end{matrix}$

The average atomic number Z of each phase is the sum of atomic masses ofeach atom present in the phase divided by the total number of atomswhere N is the number of each element of atomic number A and atomic massZ (ΣNA is the molecular weight).

$\begin{matrix}{\overset{\_}{Z} = \frac{\sum{NAZ}}{\sum{NA}}} & \left( {{Equation}\mspace{14mu} 2} \right)\end{matrix}$

The η for the phases present in the cement particles are shown in Table2. Amorphous phases have a variable chemistry not determined bydiffraction. For most cements, the amorphous phase will have acomposition similar to the melilite phase. In cements with lower Al₂O₃and MgO content the amorphous phase will have a higher mean atomicnumber and thus will exhibit a higher brightness in BSE imaging. Phaseidentities are verified by X-ray microprobe measurement of individualphases.

TABLE 2 Calculated BSE contrast values for the phases present incarbonatable calcium silicate cement particles ^(a) Phase η SiO₂ 0.127Al - Melilite (Ca₂Al₂SiO₇) 0.154 Mg - Melilite (Ca₂MgSi₂O₇) 0.154Wollastonite (CaSiO₃) 0.160 Rankinite (Ca₃Si₂O₇) 0.166 Belite (Ca₂SiO₄)0.171 ^(a) The highest value will correspond to the phase with thehighest brightness. The calcium silicate phases have the highest BSEcontrast and will be the brightest phases in a BSE image. The darkestareas in an image correspond to pores or voids filled with the carbonbased mounting resin.

Experimental cements were produced in two separate processes withdistinct chemistries. Experimental Cement 1 was produced with limestoneand sand ground to fineness of 85% passing 200 mesh. The limestone andsand were blended to obtain a bulk calcium to silicon atomic ratio ofapproximately 1. The ground and blended raw material was processed in arotary kiln to a peak temperature of approximately 1200° C. with aresidence time of 30 to 60 minutes to react the powder and producenodules of a sintered carbonatable calcium silicate cement clinkerlargely composed of carbonatable calcium silicates, melilites, anamorphous phase with a melilite-like composition and unreacted silica.The oxide composition of this cement as determined by X-Ray fluorescence(XRF) is shown in Table 3. The phase composition of this cement asdetermined by X-Ray diffraction (XRD) is shown in Table 4. A lowmagnification view of a polished cross section of clinker in FIG. 1shows discrete regions of low brightness silica surrounded by layersregions with increasing brightness, indicating a concentric organizationof high calcium reactive phases around the silica regions. FIG. 2 showsa higher magnification of such a region. FIG. 3 shows a highmagnification view of belite regions in a central region far from lowcalcium phases.

TABLE 3 Oxide composition of Experimental Cement 1 as measured by XRFSiO₂ CaO Al₂O₃ Fe₂O₃ MgO SO₃ K₂O Na₂O TiO₂ P₂O₅ Mn₂O₃ 44.9% 43.8% 5.3%1.8% 1.2% 0.3% 2.0% 0.4% 0.2% 0.1% 0.0%

TABLE 4 Phase composition of Experimental Cement 1 as measured by XRDAmor- Wollastonite Rankinite Belite phous Silica Lime Melilites CasiO₃Ca₃Si₂O₇ Ca₂SiO₄ variable SiO₂ CaO variable 15% 19% 14% 30% 5% 1% 16%

The cement clinker was then ground using a two-compartment closedcircuit ball mill. The material feed rate, ball mill rotation rate andpneumatic separator airflow were controlled to produce a ground cementwith a mean particle diameter of 12 μm. BSE images shown in FIG. 4 andFIG. 5 show various single phase and multi-phase particles.

Experimental Cement 1 was subjected to a detailed survey by SEM in BSEmode in conjunction with X-Ray microprobe analysis. The elementalcomposition as measured by X-Ray microprobe was associated with thephases identified by XRD. The atomic composition of the phases asdetermined by X-Ray microprobe is shown in Table 5. This analysisidentified an additional phase, brownmillerite or Ca₂(Al,Fe)₂O₅ as wellas two distinct partially reactive amorphous phases: A low Al contentamorphous phase, Phase 1, and a high Al content amorphous phase, Phase2. In FIG. 6, FIG. 7, and FIG. 8 the compositional data collected inconjunction with the contrast of the phases as seen in BSE images wasused to construct false-color maps of the unreacted particles. Numerousexamples of multi-phase particles of various classifications areobserved.

TABLE 5 Atomic composition of phases in Experimental Cement 1 determinedby X-Ray microprobe analysis. (Expressed as atomic %) Phase O Na Mg AlSi S K Ca Ti Mn Fe Wollastonite/ 59.5 0.0 0.0 0.6 18.7 0.0 0.3 20.8 0.10.0 0.1 Psuedo- wollastonite Rankinite 58.0 0.0 0.2 0.4 15.8 0.0 0.125.5 0.0 0.0 0.0 Belite 56.8 0.0 0.1 0.6 13.3 0.0 0.2 28.8 0.0 0.0 0.1Amorphous 62.2 0.7 0.8 0.7 36.1 0.0 4.2 4.7 0.1 0.0 0.4 (1) Amorphous60.0 0.8 0.4 9.3 18.8 0.0 6.3 4.1 0.0 0.0 0.1 (2) Brown- 55.9 0.0 0.77.0 3.3 0.4 0.3 23.9 0.4 0.1 8.0 millerite Melilite 58.3 0.4 2.1 8.812.1 0.0 0.3 17.2 0 0 0.8 Silica 66.6 0.0 0.0 0.3 33.0 0.0 0.0 0.0 0.00.0 0.0 Lime 50.0 0.0 0.0 0.0 0.0 0.0 0.0 50.0 0.0 0.0 0.0

A carbonatable calcium silicate was produced (Experimental Cement 2). Toobtain the cement limestone and sand were ground to fineness of 85%passing 200 mesh. The limestone and sand were blended to obtain a bulkcalcium to silicon atomic ratio of 1. The ground and blended rawmaterial was processed in a rotary kiln to a peak temperature ofapproximately 1260° C. with a residence time of 30 to 60 minutes toreact the powder and produce nodules of a sintered carbonatable calciumsilicate cement clinker largely composed of carbonatable calciumsilicates, melilites, an amorphous phase with a melilite-likecomposition and unreacted silica. The oxide composition of this cementas determined by XRF is shown in Table 6. The phase composition of thiscement as measured by XRD is shown in Table 7. A polished clinker inFIG. 9, FIG. 10, and FIG. 11 shows discrete areas of a silica phasesurround by a layered microstructure of increasing brightness reactivematerials. In FIG. 12 and FIG. 13 elemental maps of Si and Ca aresuperimposed over FIG. 11 showing the change in Si and Ca contentthrough the microstructure. In FIG. 14, an elemental map of K issuperimposed over FIG. 11 showing that amorphous material with acharacteristically high K content is present in between the Si rich coreparticle and Ca rich reactive phase layer.

TABLE 6 Oxide composition of Experimental Cement 2 as measured by XRFSiO₂ CaO Al₂O₃ Fe₂O₃ MgO SO₃ K₂O Na₂O TiO₂ P₂O₅ Mn₂O₃ 43.8% 42.9% 6.0%2.5% 2.0% 1.0% 1.1% 0.1% 0.3% 0.2% 0.1%

TABLE 7 Phase composition of Experimental Cement 2 as measured by XRDAmor- Wollastonite Rankinite Belite phous Silica Lime Melilites CasiO₃Ca₃Si₂O₇ Ca₂SiO₄ variable SiO₂ CaO variable 23% 18% 1% 23% 5% 0% 30%

In this specification and the appended claims, the singular forms “a,”“an,” and “the” include plural reference, unless the context clearlydictates otherwise.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art. Although any methods and materials similar or equivalent tothose described herein can also be used in the practice or testing ofthe present disclosure, the preferred methods and materials are nowdescribed. Methods recited herein may be carried out in any order thatis logically possible, in addition to a particular order disclosed.

INCORPORATION BY REFERENCE

References and citations to other documents, such as patents, patentapplications, patent publications, journals, books, papers, webcontents, have been made in this disclosure. All such documents arehereby incorporated herein by reference in their entirety for allpurposes. Any material, or portion thereof, that is said to beincorporated by reference herein, but which conflicts with existingdefinitions, statements, or other disclosure material explicitly setforth herein is only incorporated to the extent that no conflict arisesbetween that incorporated material and the present disclosure material.In the event of a conflict, the conflict is to be resolved in favor ofthe present disclosure as the preferred disclosure.

Equivalents

The representative examples disclosed herein are intended to helpillustrate the invention, and are not intended to, nor should they beconstrued to, limit the scope of the invention. Indeed, variousmodifications of the invention and many further embodiments thereof, inaddition to those shown and described herein, will become apparent tothose skilled in the art from the full contents of this document,including the examples included herein and the references to thescientific and patent literature cited herein. These examples containimportant additional information, exemplification and guidance that canbe adapted to the practice of this invention in its various embodimentsand equivalents thereof.

1. A non-hydraulic clinker material, comprising particles ofuncarbonatable silica (SiO₂) dispersed in a matrix comprising at leastone carbonatable calcium silicate phase comprising at least one ofwollastonite and pseudowollastonite.
 2. The clinker material of claim 1,further comprising: an intermediate layer, comprising melilite((Ca,Na,K)₂(Al,Mg,Fe)[(Al,Si)SiO₇]) and/or an amorphous phase andsurrounding the particles of uncarbonatable silica.
 3. The clinkermaterial of claim 2, wherein the matrix comprises rankinite (Ca₃Si₂O₇)and/or belite (Ca₂SiO₄).
 4. The clinker material of claim 3, wherein theintermediate layer comprises an amorphous phase comprising one or morecomponents selected from Al₂O₃, Fe₂O₃, MgO, K₂O and Na₂O.
 5. The clinkermaterial of claim 1, wherein the matrix further comprises one or morecomponents selected from Al₂O₃, Fe₂O₃, MgO, K₂O and Na₂O.
 6. The clinkermaterial of claim 1, wherein the uncarbonatable silica particles havediameters from about 0.1 μm to about 1,000 μm; and the intermediatelayer has a thickness from about 0.1 μm to about 250 μm.
 7. (canceled)8. (canceled)
 9. The clinker material of claim 1, wherein elemental Caand elemental Si are present in the clinker at an atomic ratio fromabout 0.8 to about 1.2.
 10. (canceled)
 11. The clinker material of claim1, wherein the clinker is suitable for carbonation with CO₂ at atemperature of about 30° C. to about 90° C. to form CaCO₃, under anatmosphere of water and CO₂ having a pressure in the range from ambientatmospheric pressure to about 150 psi above ambient and having a CO₂concentration ranging from about 10% to about 99% for about 1 hour toabout 150 hours, with a mass gain of about 10% or more.
 12. The clinkermaterial of claim 11, wherein the clinker is suitable for carbonationwith CO₂ at a temperature of about 40° C. to about 80° C. to form CaCO₃,under an atmosphere of water and CO₂ having a pressure in the range fromambient atmospheric pressure to about 40 psi above ambient and having aCO₂ concentration ranging from about 50% to about 95% for about 10 hourto about 50 hours, with a mass gain of about 10% or more.
 13. Theclinker material of claim 5, comprising about 30% or less of metaloxides of Al, Fe and Mg by total oxide mass.
 14. (canceled)
 15. Acomposite material produced by carbonation of a clinker material ofclaim
 1. 16. A method for making a clinker material, comprising: mixingone or more precursors to obtain a blended precursor composition whereinelemental Ca and elemental Si are present at an atomic ratio from about0.8 to about 1.2 and metal oxides of Al, Fe and Mg are present at about30% or less by mass; and heating the blended precursor composition to atemperature between about 800° C. and about 1400° C. for a sufficienttime to produce the clinker material.
 17. The method of claim 16,wherein metal oxides of Al, Fe and Mg are present at about 10% or lessby mass.
 18. The method of claim 16, wherein the precursors are selectedfrom limestone, sand, silts, sandstones, silica-rich clays anddiatomaceous earths.
 19. (canceled)
 20. The method of claim 16, whereinthe blended precursor composition is heated to a temperature betweenabout 900° C. and about 1,300° C. for a sufficient time to produce theclinker material.
 21. The method of claim 16, wherein the blendedprecursor composition is heated for a period of about 10 minutes hour to5 hours.
 22. (canceled)
 23. (canceled)
 24. The method of claim 16,wherein heating the blended precursor composition is conducted underatmospheric pressure.
 25. A powdery material produced by grinding theclinker material of claim 1, wherein the powdery material ischaracterized by a mean particle size (d50) of about 8 μm to about 25μm, with 10% of particles (d10) sized below about 0.1 μm to about 3 μm,and 90% of particles (d90) sized between about 30 μm to about 100 μm.26. The powdery material of claim 25, wherein the powdery material ischaracterized by a surface at least 10% covered with the at least onecarbonatable phase.
 27. (canceled)
 28. (canceled)
 29. The powderymaterial of claim 25, wherein the particles comprise single-phaseparticles and multi-phase particle.
 30. (canceled)
 31. (canceled)